iOS: Stylesheet/Theme for iOS app

For one of my apps I currently allow for custom themes if the client makes a request (which they usually do, as it's a branded application). Sometimes this can be as simple as simply changing the colour scheme so I was wondering if there was a way to simplify the process. For example, if I had a class named ColourStyle and I specified its colour property values and then imported it to other classes, could I simply set it up so all I have to do is edit this one class and the others will naturally base their colours on whatever value is set in ColourStyle?